Surface modified nylon fibers produced by photocatalyzed halogenation



United States Patent Oflice 3,549,306 Patented Dec. 22, 1970 3,549,306 SURFACE MODIFIED NYLON FIBERS PRODUCED BY PHOTOCATALYZED HALOGENATION Herbert N. Friedlander, Raleigh, and Virginia C. Meuikheirn, Chapel Hill, N.C., assignors to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Jan. 6, 1966, Ser. No. 518,979 Int. Cl. D06c 1/08; D06m 3/30 US. Cl. 8-1155 8 Claims ABSTRACT OF THE DISCLOSURE Nylon fibers are treated with chlorine, bromine, iodine or mixtures thereof and subjected to irradiation with light having wavelengths in the range of about 3000 to 4000 angstroms to improve the surface wettability thereof.

This invention relates to novel synthetic textile fibers of nylon and to the processes for their manufacture.

An object of this invention is to provide novel nylon textile fibers having improved properties which fibers are useful in the manufacture of yarns and fabrics.

Another object of this invention is the provision of a modified nylon fiber wherein said modification occurs without substantially degrading the bulk tensile properties of the fiber. Still a further object of the invention is to provide a continuous process for modification of nylon fibers which can be adapted to commercial manufacture of nylon fibers without disruption of the continuity of the overall manufacturing process.

It has been discovered that the surface properties of nylon fibers can be significantly modified by rapid halogenation of a preformed fiber of a nylon polymer such that the concentration of halogen attached to the surface of this resulting fiber ranges from about 50 to about 5,000 parts by weight per million parts of fiber. In accordance wtih this invention the concentration halogen bound to the fiber is essentially limited to the surface of the fiber or to the fiber skin so that the bulk tensile properties of tenacity and elongation are not substantially modified. Useful products are obatined Where the halogen is chemically bonded to the nylon molecules occurring on the surface of the fiber in the form of covalent bonds, i.e., halogen substitution on carbon; coordinate bonds, i.e., where a diatomic halogen-amide group adduct or a charge transfer complex is formed, and both covalent and coordinate bonds in the sense above described.

One method employed for nylon fiber modification comprises passing the fiber through a halogen atmosphere in the absence of an initiator in such a manner that the concentration of halogen and period of residence does not allow dilfusion of the halogen into the core of the fiber, but rather limits the reaction to the surface of the fiber. This process results in a modified fiber wherein the halogen is bonded to the surface or skin of the fiber predominantly in the form of a halogen-amide group adduct which may otherwise be described as a charge transfer complex. Exposure of the product formed by the above described porcedure to ultraviolet or other energy source results in rearrangement of the halogen atoms such that a portion of the coordinate bonded halogen atoms substitute on the surface molecules in the form of a covalently bonded halogen.

Another method for forming the surface modified fibers of this invention wherein halogen is found bonded both in the form of a substituent and as an adduct resides in simultaneously subjecting the preformed nylon fiber to the action of halogen and an initiator for halogenation, such as ultraviolet light.

The light accelerates the formation of the diatomic chlorineamide adduct as well as forms chlorine atoms which react with the hydrocarbon portion of the chain to substitute chlorine on the carbons oz and 3 to the amide nitrogen. These conclusions are verified on the NMR spectra of chlorinated and photo-chlorinated N,N-dipropyl succin amide which was used as a model compound.

While it has been determined that the covalently bonded halogen atoms are permanent in the sense that they are not removed by washing, laundering and other conventional textile treatment, it has been discovered that the halogen present on the surface of the fiber in the form of a halogenamide group adduct can readily be removed by washing with water, or by extraction with polar organic solvents, such as methanol. Reversibility of the adduct formation provides a route for temporary disruption of the physical state of the surface layers of nylon fibers.

The modification of nylon fibers occasioned by the presence of halogen bound to the polymer molecules results in increased wettability of the fiber surface. This property is beneficial in several respects in that wearing apparent which cannot adequately transfer moisture and/or moisture vapor away from the body is uncomfortable, etc. Increased wettability of the fibers of this invention results in a more silk-like feel to the wearer. Moreover, this property is permanently built into the fiber and does not suffer diminution upon ordinary laundering as do many hydrophilic finishes.

Another benefit derived from the modified fiber of the invention based on increased wettability resides in the enhanced adherence to the fiber surface of amine and other types of finishes.

Another and distinctly different benefit derived from the product of this invention is that the chemically bonded halogen atoms on the surface of the fiber represent sites for secondary reactions involving further fiber modification. Thus, primary and secondary, mono and polyamines may be reacted with the chlorine atom substituted on the surface of the fiber to further substitute or modify the chemistry of the fiber surface. Amines so substituted have been quaternized to enhance to anti-static properties of the filament in a manner similar to conventional anti-stat finishes. In the instant invention the molecular groups which provide anti-static properties to the fiber are permanently and chemically bonded .to the fiber whereas prior art anti-static agents generally have been applied as coatings which are subject to removal in ordinary use.

While modification of surface properties occur over a broad range of halogen concentrations on the fiber surface, changes become more pronounced in the higher ranges. Moreover, secondary reactions occur with greater ease where the occurrence of halogen reaction sites is greater. This is not to say, however, that beneficial properties are not observed at levels of halogen which are quite low. The limiting factor with respect to the level of halogen appears to be the highest concentration possible without serious degradation of the bulk tensile properties of the fiber and this may be governed by the particular use intended for the fiber.

The materials used to form the fibers having a modified surface structure according to this invention are conventional nylon or linear polyamide materials such as those described in United States Patents 2,071,230, 2,071,253 and 2,130,948. These materials are well known in the 275 C. The polymer melt is allowed to equilibrate for Y 30 minutes at 275 -280 C. and then spun through a four-hole spinnerette.

Chlorination art and are usually formed by reaction of suitabe dicar 5 The apparatus used for Chlorination consisted f a boxylic acids with suitable diamines or by polycondensa- 31/2" X VYCOI glass tube With a 71/2" p end metal tion of suitable monoamino monocarboxylic acids or deextension at the bottom Extending laterally 0111 the rivatives thereoh Methods f h fo ti f fiber tension is a 4" flexible exhaust tube leading to the laborayarns, knitted fabrics and woven or non-woven fabrics 10 y hOOd- A miXttlI? of 2 and 2 is metered through f nylon polymers are l known i h n d r a polyethylene tube situated so that it lies vertically on the not a part of this invention. It is intended, however, that inside glass wall With theh exit about. from the p fiber modification may occur according to the practice of herette facet At about from Side Of the glass tube this invention at any stage in the processing of the fibers is Placed an 3 Watt ultraviolet p WhOSe l Wave to form fabrics or on the fabric itself. length is 3650 angstroms- The terms fibers and filaments are used interchangeably Chlorine and nitrogen are introduced at rates f herein to connote staple length or continuous filamentary 3. X 10* and 28x10 f respectively, 50 that structures of nylon polymers useful for textile or other the atmosphere inside the tube is p d every minute li i and 57 seconds. The fiber is ordinarily taken on bobbins The preferred process fo the surface difi ti f at a rate of 157 ft./min. or a residence time of 0.48 secnylon fibers according to this invention involves photo- 011d inside the chlorination tubehalogenation wherein the fiber is subjected to halogen in Control filament was p n an e al manner in the presence of ultraviolet light for a period of less than the absence of chlorine and ultraviolet lightabout two seconds. The halogen may be present in an alluminated chamber through which the fiber, yarn or PROPERTIES OF CONTROLAND CHLORINATED SAMPLES other fiber containing article is continuously passed. The Draw Elongation Percent halogen may be diluted, if desired, by nitrogen or other ratio percent Tenacity Modulus c inert gas. The light source may be other than ultraviolet providing theintensity is adequate to affect photochemical illl iliatiill' 26 5 3 2% 935 22 3.21 halogenation. Generally speaking, bulks emitting light 30 ,Toolowtodetect having wave lengths in the range between 3300 and 4800 angstroms are suitable. The essential feature of the process is that the conditions be so correlated that the reaction The Pe,rc.ent equivalent 2 Parts occurs only on the surface or skin 6 the fiben per milhon. In similar examples chlorination levels The halogen should not be allowed to diffuse into the reached, 4000 but filament Physlcal Propertles are core of the fiber because interior penetration is likely to not avallfible for these degrade the bulk tensile properties of the fiber and thereby ht reductlon P appreclable- However offset the beneficial aspects of surface modification. tenaciues 9 3 5 are sun afieqflate for most uses;

The term halogen as herein used is intended to include and, If desired, one can hold chlorination to a lower level, those halogens having an atomic number between 17 and 40 holdmg g loss also to a lower level and Sun get Thus, chlorine, bromine, iodine and mixtures thereof, reasonably slgmficant surface effects and a reasonable such as a mixture of chlorine and bromine are useful in concentration of sites for secondary reactlonthe preparation of the modified halogenated products of EXAMPLE H this invention.

EXAMPLE I 5 A polymer of nylon 66 having a relative viscosityof 0.7, 52.4 10- eq./gm. of carboxyl end groups and yolymenzatlon 59.3 10'- eq./gm. of amine end groups was spun into About 175 grams hexamethylene ammonium adipate monofilament and then drawn without application of and 58ml. water are charged to a high pressure stainless finish. Several samples of the filament were passed through steel autoclave and purged with nitrogen. The contents a glass tube having an atmosphere rich with gaseous are heated to 243 C. while maintaining a pressure of chlorine and exposed as indicated to the light of a 4 watt 250 p.s.i.g. During this period the reaction mixture is conblack light lamp emitting light having wave lengths rangtinuously agitated by means of a stirrer. The pressure is ing from 3000 to 4000 angstroms. The results of the sevreduced to atmospheric over a 25 minute period while eral runs where determined are indicated in the following the temperature of the reaction mixture approaches table.

TABLE Exposure,

seconds Oh flow 01 T t E t1 Ch Light ca ee. analysis Denier, g. Modulus g/d. ci rc iit 1 After H20 extraction.

2 Control, not chlorinated or exposed to light.

We claim:

1. A halogen modified nylon fiber wherein said halogen is attached to polyamide molecules essentially on the skin or surface of the fiber in amounts ranging from about 50 to about 5,000 parts by weight per million parts of fiber, produced by passing a nylon filament through an atmosphere comprising a reactant consisting of chlorine, bromine, iodine or mixtures thereof and subjecting the filament to irradiation with light having wavelengths in the range of from about 3000 to 4000 angstroms.

2. The fiber of claim 1 wherein the halogen is chlorine.

3. The fiber of claim 2 wherein the chlorine atoms are chemically attached to the fiber surface by covalent bonds or coordinate bonds or both covalent and coordinate bonds.

4. The fiber of claim 3 wherein the chlorine is attached to the fiber surface by covalent bonds.

5. The fiber of claim 3 wherein the chlorine is attached to the fiber surface by coordinate bonds.

6. The fiber of claim 3 wherein said chlorine is attached to the fiber surface by both covalent and coordinate bonds.

7. The fiber of claim 1 wherein the halogen is bromine. 8. The fiber of claim 1 wherein the halogen is a mixture of chlorine and bromine.

References Cited GEORGE F. LESMES, Primary Examiner I. CANNON, Assistant Examiner US. Cl. X.'R. 

